1. Field of the Invention
The present invention relates to a new type of dental syringe.
2. Description of the Related Art
In the dental syringe art, the conventional syringe is adapted to allow the dentist to retract the syringe plunger after the initial stick, in order to ascertain that he has not hit a blood vessel, by using his thumb in the thumb ring of the syringe, pulling back on the plunger and observing the anesthetic vial to determine if blood has been pulled into the syringe. If it has, this indicates that he must find a new spot for the injection point in order to avoid injecting anesthetic into the bloodstream via a blood vessel. There are two reasons for this:
One is that the anesthetic usually contains epinephrine, which can affect heart rate adversely.
Two, is that if the anesthetic is taken away from the site by the blood vessel, it will fail to anesthetize the site.
Thus, in contrast to the usual medical syringe used by doctors, in which the entire syringe is generally disposable, the dental syringe has a reusable metal framework.
FIG. 1 shows the prior art in which the syringe comprises a metal body which is open on one side to admit a clear plastic anesthetic vial, in the form of a cylinder containing local anesthetic, sealed in by a penetrable seal at the needle end, and by a sliding, flexible seal at the plunger end of the syringe. The plunger comprises a thumb ring, a shaft, and a harpoon at the vial end of the shaft. In operation, the vial is inserted into the metal body. The metal body is placed threaded end down to a surface. An impact is applied to the end of the thumb ring to drive the harpoon into the sliding rubber seal. The needle is then screwed by the screw threads onto this threaded end of the syringe so that the medicine penetrator, which is basically a short needle, penetrates the end seal of the vial. Medicine can now be injected, or the plunger barbs can pull back, to test for the needle point""s proximity to a blood vessel, by pulling blood into the medicine vial which will be visible to the dentist.
A problem of the prior art is that the threads of the needle must be a tight fit, which makes the needle quite difficult to remove from the threads of the metal body. This is complicated by the fact that the needle is a sharp object covered with human blood, containing human blood, and presenting a significant biohazard if the operator is stuck by said needle. The operator typically must apply large amounts of force to remove the needle from the metal body, with the operator""s hands in close proximity to this hazardous sharp object.
U.S. Pat. No. 3,848,593 to Baldwin refers to an alternative needle securement, but still requires an application of significant rotational torque at the needle.
The present invention seeks to obviate this problem by having a non-threaded needle mount.
It is an object of the present invention to provide a syringe which obviates the need to apply an unscrewing force in the vicinity of the needle which exceeds the breaking strength of the sharp contaminated needle. The invention provides an easy side loading syringe from which the needle assembly is easily removed.